Articulation is the term for the configuration of bridge supports and choice of structural bearings that provides the necessary restraints to the superstructure whilst at the same time providing freedom to some displacements and rotations in order to avoid unnecessary forces on both the superstructure and substructure due to constraint. A range of different bearing types is available. Selection of the appropriate type and specification of the forces they must resist and displacements they must permit is a key responsibility for the structural designer. Clear communication of the requirements for the bearings and for their installation is essential for proper functioning of the structure and for avoidance of unanticipated maintenance issues. Bearings are used to transfer forces from the superstructure to the substructure whilst either tolerating or constraining relative movement.
This might cause websites not to be displayed properly. Customized Bridge Neoprene Rubber Bearing. Larger movements require taller bearings and possibly additional mechanical Elastomeric strip bearing of preventing the bridge deck from effectively floating from the desired position. Beafing displacements at supports arise beaeing from an overall Elastomeric strip bearing in length of the structure and due to bending in a vertical plane since the centroidal axes are above the levels of the supports. CDM Making your world a quieter place. Details of these type Pic of gay bridge installations Elastomeric strip bearing be supplied on request. Algeria Angola. Spherical bearings are used to accommodate large rotations by the use of a lower spherical surface.
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Highly skilled Elastomeric strip bearing baering team for bespoke structural installation - we thrive on a challenge. Thermal actions. They provide beariing isolation and are generally simple to install. Drill Riser Buoyancy. The schedule should contain the following information:. Impact Protection. A sliding surface can be included to accommodate translational movement, which can be in any direction or constrained by guides. It is not normally required to fix the bearing in place as friction between the Fuck up girls and the support surfaces will normally be adequate. Common Mistakes. Please try again.
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- Ekspan is the UK's largest quality bearing supplier and installer to meet demands both in the UK and worldwide.
- Trelleborg bearings mainly play a role in relieving load movement or noise reduction.
- Non-reinforced bearing devices are best specified when the load, rotation and horizontal deflection are minimal.
- Compared to other types of bearings, they are easy to install, have a long life expectancy — years plus — and are maintenance free.
Ekspan is the UK's largest quality bearing supplier and installer to meet demands both in the UK and worldwide. Ekspan supply an extensive range of mechanical and elastomeric expansion joints and seal joints, where the majority have Highways England SA-1 accredited approval. ECI involvement on new and bespoke contracts. Ekspan have carried out a number of projects for swing bridges and foot bridges.
From design, fabrication of all structural components, to trial erection and final installation. Details of these type of bridge installations can be supplied on request. Natural Rubber strip can be utilised to support a concrete diaphragm and natural rubber pads are used to support individual beams. Prime Resins Americas International. Link Bearing BS Bespoke Bearings.
Trelleborg Offshore - Rochdale, UK. Sliding elements. Bearings are used to transfer forces from the superstructure to the substructure whilst either tolerating or constraining relative movement. As bearings and expansion joints introduce a maintenance liability, it is good practice to limit the number of bearings required and to minimise the movement to be accommodated by an expansion joint. Trelleborg Offshore - Krokstadelva, Norway.
Elastomeric strip bearing. SEE US ON STAND A50 AT TRAFFEX SCOTLAND
Laminated bearing assemblies are molded to any shape or size. The internal steel plates are vulcanize-bonded to alternating layers of elastomer during the molding process. The addition of a low-friction sliding surface allows a standard laminated elastomeric bearing device to accommodate unlimited horizontal displacement without increasing the height of the bearing assembly.
A slide bearing assembly consists of an upper and lower component. The upper component consists of a steel load plate attached to the superstructure and a polished stainless steel sheet welded to the load plate. From design, fabrication of all structural components, to trial erection and final installation. Details of these type of bridge installations can be supplied on request. Highly skilled and pro-active team for bespoke structural installation - we thrive on a challenge.
The presentation focuses on our diverse and market leading range of bridge deck expansion joints and structural bearings. We provide full product and site support — from design, manufacture and installation, to inspection, site maintenance and replacement work. Our depth of knowledge and expertise enables us to provide structural solutions by way of consultancy support or the delivery of a complete project management service.
Removal of 65no rocker bearings. Design, manufacture, supply and installation of 65no mechanical pot bearings. Prime Resins Americas International. View Bearings.
Versiflex™ Elastomeric Bearing Assemblies | D.S. Brown
Articulation is the term for the configuration of bridge supports and choice of structural bearings that provides the necessary restraints to the superstructure whilst at the same time providing freedom to some displacements and rotations in order to avoid unnecessary forces on both the superstructure and substructure due to constraint.
A range of different bearing types is available. Selection of the appropriate type and specification of the forces they must resist and displacements they must permit is a key responsibility for the structural designer. Clear communication of the requirements for the bearings and for their installation is essential for proper functioning of the structure and for avoidance of unanticipated maintenance issues.
Bearings are used to transfer forces from the superstructure to the substructure whilst either tolerating or constraining relative movement. The principal actions that give rise to displacements and rotations at supports are:. Generally, the structure will rotate about longitudinal and transverse axes at its supports and these rotations must either be accommodated in the bearings or the bearings must be designed to resist them in which case the effects on the structure must also be considered.
In some cases, there is also a rotation about a vertical axis associated with plan bending of the structure but this is usually small in magnitude.
Horizontal displacements at supports arise both from an overall change in length of the structure and due to bending in a vertical plane since the centroidal axes are above the levels of the supports. The following recommendations relate to the articulation arrangements for typical highway bridges. As bearings and expansion joints introduce a maintenance liability, it is good practice to limit the number of bearings required and to minimise the movement to be accommodated by an expansion joint.
Spans should be arranged so as to avoid uplift at bearing positions it is a very complex and costly matter to provide restraint against uplift in a bearing , particularly when dealing with skewed structures. The designer should avoid locking in forces that would hinder bearing replacement. Restraint against longitudinal forces should be provided at one support, with guided restraints aligned to allow movement at the other supports.
Similarly, restraint against transverse forces should be provided at only one bearing at each support. The construction sequence of the structure should also be considered, to establish the permanent displacements. The articulation scheme that the designer chooses should be shown on the drawings and will form the basis of a bearing schedule.
The convention for illustrating the movements and constraints in bearings is given in Table 1 of BS EN . A selection of common symbols is given below. The symbols for elastomeric pot bearings will be solid black, rather than an open square and circle. The bearings for this articulation arrangement will be elastomeric bearings.
All horizontal forces and movements are then accommodated by shear deformation of the bearings. The arrangement above shows the layout for a simple single span structure with skew. The bridge deck is fixed in one corner and horizontal movements are controlled by the use of guided unidirectional bearings. A free multidirectional bearing is provided for the diagonally opposite corner to the fixed bearing.
In a wider deck, it would be preferable to locate the fixed bearing closer to the centre of the deck so as to minimise the relative transverse movement and thus limit the movements to be accommodated by the expansion joint. For longer spans, the magnitude of the movements increases and therefore these should be minimised by locating the fixed bearing at the centre of the bridge to ensure the thermal expansion is split between each end of the bridge.
Care should be taken to ensure that the pier is designed for the resulting horizontal forces, particularly from braking and acceleration actions. On multi-span structures, care should be taken to ensure movements are not restrained, however the use of slender piers that are able to flex may allow for load sharing between bearings at a support location. Further examples of bridge articulation arrangement are given in Guidance Note 1. Curved decks can be guided either radially from a fixed point or tangentially to the radius of curvature.
If the deck is guided radially, then the accuracy of the geometry becomes critical for the bearings furthest from the fixed point. For structures with a constant curvature it is best to align the bearings tangentially to effectively guide the deck around the curve as it expands and contracts. The resulting horizontal forces are often accommodated by the use of specific guide bearings which may not be vertical load carrying. At road level, these movements are accommodated by an expansion joint, which isolates the abutments from the displacements and maintains the integrity of the surfacing at the end of the bridge.
The bridge designer should specify the expansion joints in a similar manner to bearings , giving details of characteristic and design values of displacements to the joint designer. Annex B of BS EN  contains guidance for the preparation of a technical specification for expansion joints.
By introducing bearings , and particularly by introducing expansion joints at road level, a significant maintenance liability is created. This reduces, and in some cases eliminates, the need for maintenance but the designer must still consider the movements displacements and rotations that are induced by traffic and thermal actions and make appropriate allowances.
The product standard for bearings is BS EN and this is the standard referred to in the Eurocodes. The choice of bearing will be governed by both the values and directions of the actions and also by the magnitude and directions of the allowed and restrained displacements. Typical load bearing capacities at ULS are tabulate below. Further guidance on the types of bearings and their usage can be found in Guidance Note 3.
Elastomeric bearings normally consist of a number of rubber layers separated by steel plates. These are normally laid in pads or strips and are ideally suited for small structures. They accommodate movements by deformation. It is not normally required to fix the bearing in place as friction between the rubber and the support surfaces will normally be adequate.
Elastomeric bearings provide an excellent economic solution for applications where structure movements, longitudinal, transverse and rotational are small. They provide vibration isolation and are generally simple to install. Elastomeric bearings are relatively maintenance free but will degrade over time and require replacement.
Larger movements require taller bearings and possibly additional mechanical means of preventing the bridge deck from effectively floating from the desired position. When used on steel bridges , elastomeric bearings can be positively located using perimeter keep strips welded to the underside of the bottom girder flange. The elastomeric pot bearing consists of a confined disk of elastomer within a short cylinder the pot.
This puts the elastomer under high pressure, making it behave like a liquid, permitting rotation in any direction with very little resistance. A sliding surface can be included to accommodate translational movement, which can be in any direction or constrained by guides. The rotations and the translations, as well as the loads carried, can be greater than for elastomeric bearings.
Spherical bearings are used to accommodate large rotations by the use of a lower spherical surface. This is normally lined with dimpled PTFE and matched to an upper stainless steel surface. Generally, these bearings require a minimum co-existent vertical load to prevent instability. These bearings allow rotation about a single axis usually transverse to the girder.
They are often used when impact loading is high, such as on railway bridges. These types of bearings are occasionally used on heavily skewed or multispan structures. The schedule should contain the following information:. The bearing designer normally the manufacturer will then use this information to determine the design values and therefore the full specification.
There are currently two alternative templates given for the bearing schedule, one is given in Table A. Table A. Generally, the bearing designer will be unaware of the relevant design combinations and will thus not be able to determine design values for the bearings from these characteristic values. Table B. This schedule also requires reference data, maximum dimensions and fixing details to be indicated.
This deficiency will be addressed in the planned Amendment to BS EN  , which will give new schedule tables. The designer must be aware of the difference between the two schedules and ensure that adequate information is supplied to the bearing supplier. It is also important, for correct installation , that the orientation of the bearing is clear; see advice in Guidance Note 2.
It is important to note that, for steel bridges , the bearings are normally installed before completion of the bridge deck and therefore bearings will have to accommodate additional thermal displacements and also movements due to construction activities. A common situation that must be considered is rotation due to pre-camber and the drop-out during construction, particularly in heavily skewed structures where may be large transverse rotations at the supports.
These rotations are a function of the plan geometry and are related to the magnitude of the dead load effects and the pre-camber provided, they cannot be avoided. Bearings are normally bolted to the girders above and the substructure below to allow replacement.
The bearings are normally bolted through the girder bottom flange though difficulties do arise with thick flanges and moderate to large gradients since it is only feasible to drill square to the flange surface. A common solution to this problem is to use tapped holes in the taper plate, which is then welded to the underside of the girder; when using this detail, the horizontal forces on the bearing need to be minimised.
Refer to Guidance Note 2. Skew ladder deck being lowered onto an elastomeric pot bearing Image courtesy of Arup. Attachment of bearing by bolting through girder flange.
An estimate for the initial installation temperature for the installation of the bearing should be given by the designer to the constructor enable the bearing to be set correctly prior to installation, in order to allow the full expansion and contraction displacements to be accommodated.
Some guidance for this installation temperature and the associated temperature range is found in the Eurocodes but there remains some potential confusion. The following is an attempt to guide the designer through the relevant parts of the Eurocodes relating specifically to bearings and expansion joints as the onus is on the designer to specify the range of displacement at the ultimate limit state. However, clause NA. It is sensible to give the assumed installation temperature, so as to reduce the temperature range of the bearings — a value should be selected to be such that the temperature expansion and temperature contraction are similar i.
As the designer should use the temperature ranges given to estimate the maximum reversible displacements, there is scope for conservatism here without undue cost. Further guidance on how designers should calculate the movement range to be specified for bridge bearings, taking account of both thermal change and uncertainty in the relative positioning of bearings on the sub- and superstructures, is available in SCI P Clause A.
To achieve this, access for inspection must be provided, there must be means to relieve the bearings of load, and it must by physically possible to extract the old and insert a new bearing. At an abutment, a common design feature that facilitates inspection and maintenance of the bearings is the abutment gallery. An example of the arrangement for a composite bridge is shown right.
Navigation menu Home. Share Tweet. Tools Printable version. From SteelConstruction. Typical elastomeric pot bearing under a steel girder. Floating bearing layout single span on elastomeric bearings. Simple bridge bearing layout single span on pot bearings.